1. Field of the Invention
The present invention relates to a system for forming either a lateral passageway at a desired location in a well bore or for forming a sharply curved continuation thereof. The invention provides a guide apparatus which may be introduced into the well bore along with the drilling means and which, at the desired level, may be activated from the surface to deflect the drilling means in the desired direction.
2. Description of the Prior Art
Current oil field practice in drilling deviated full diameter wells, that is wells formed by the largest diameter bit that will pass through the last string of casing set, is to develop deviation angle at a rate of a few degrees per 100 feet of new hole. Rarely, angle increase may reach 7 to 9 degrees per 100 feet. Because sharply curving well bores may be formed with the instant apparatus and appropriate boring tools it is more convenient to relate change in angle to the number of hole diameters drilled. Thus, a buildup angle of 10 degrees per 100 feet in a 8.25-inch hole is the same as one degree per 14.5 diameters. The instant invention contemplates well curvatures of the order of magnitude of 2 to 8 times the minimum bending radius of the flexible shaft. For example, the manufacturer of a 4-inch inside diameter hose having a theoretical burst pressure of 4,000 pounds per square inch recommends a minimum bending radius of 16 inches for that hose. Such hose may be used in forming an 8.25-inch diameter lateral bore which curves 90 degrees in 6 diameters, or 15 degrees per well diameter. The boring tool preferably is self-advancing and must be able to penetrate the earth when deflected laterally by the guide. Boring means described above are the subject of my copending application Ser. No. 06/125,240 filed Feb. 27, 1980.
U.S. Pat. No. 1,660,999, MacDonnell, describes an apparatus having a laterally deflectable guide portion and a flexible shaft with a drill bit at its lower end. The device requires an anchor pipe to the well bottom and an under reamed well section and is not capable of forming a full diameter bore hole.
In the field of solution mining Cross, U.S. Pat. No. 2,251,916, shows a curved roller and cable guidance system for directing a small diameter, solvent carrying hose, which may include an advancing means and a turbo-cutter. The system appears incapable of forming a full diameter, curved bore hole, although a large cavity may be made in a sufficiently soluble stratum.
U.S. Pat. No. 2,271,005, Grebe, combines solvent and boring apparatus to form a passageway from a vertical well. While several orienting and hose bending guides are illustrated, it is clear that the system is unable to form a full diameter, lateral bore hole.
U.S. Pat. No. 2,516,383, Hays, shows a hose turner having an endless belt and a curved passageway with flanged rollers for extending a conduit outwardly from a first well to drill a lateral bore hole. The apparatus is unable to form a full diameter bore and is too complicated for practical usage.
The drilling means of Robertson, U.S. Pat. No. 2,516,421, includes an electrically powered drive system for bending a flexible shaft. The length of lateral hole which can be formed by the Robertson device is quite limited since no means of re-entry is shown. Also, a full diameter lateral bore is not possible with this device.
U.S. Pat. No. 2,822,158, Brinton, discloses a method of fluid mining including a shaft bendable in one plane but not in a plane normal thereto. A boring device is shown to carom off a rounded top of a post which is claimed to act as a deflector to cause a horizontal and even an upwardly trending bore to be drilled. The method is limited to a very special condition of earth stratification rarely, if ever, found in real life. No means for orienting a boring tool is disclosed.
U.S. Pat. No. 3,402,965, Dahms et al, describes an improved method of solution mining including an orientation means and a floating solvent delivery hose which extends itself by internal fluid friction to convey a solvent to the nether reaches of a solution cavity. Boring is not disclosed and the system appears incapable of adaptation to a boring operation.
U.S. Pat. No. 3,402,967, Edmonds et al, relates to a solution mining apparatus employing a nest of tubes to be extended at right angle to a bore hole. Because the nest of tubes requires a cavity in order to be extended, the apparatus is unsuited to boring.
J. A. Zublin in U.S. Pat. Nos. 2,336,334 and 2,382,933 shows systems for drilling deviated holes using a specially designed slotted section of drill pipe just above the bit. The slotted section is so constructed as to normally assume a curved position but is held straight while being lowered into the well bore by a rigid internal rod. Once deviation is attained, the Zublin device must be removed from the hole before further drilling can proceed with attendant hazards of stuck drill pipe.
Other devices for deflecting a drilling bit are shown by S. Shinomiya, U.S. Pat. No. 2,410,753; Roy Cullen, U.S. Pat. No. 3,903,974; and John D. Jeter in U.S. Pat. Nos. 3,893,523 and 4,007,797. Shinomiya proposes to deviate the flexible pipe section at the end of his drill string by pulling on a cable from the surface. The practicality of such a scheme is questionable. As shown his device seems intended to produce an enlarged section, similar to underreaming, at the bottom of a bore hole. Cullen and Jeter are generally similar to Zublin in that they propose the use of specially designed sections to be inserted in the drill string just above the bit to attain the desired deflection of the bit.